Enhancement of low light images has drawn much attention in the field of computational photography. Images captured under low light conditions are underexposed, suffer from noise and color cast, and lack fine features. In order to obtain high sensitivity under low light conditions, a high ISO setting is required, which leads to a large amount of noise in the captured images. Another approach to tackle this problem is to use an external light source (e.g., a flash) when capturing the images. However, as the color temperature and the intensity of a flash differ from those of the ambient atmosphere, use of a flash may result in unnatural artifacts such as red eye, harsh shadows, etc.
Several methods for enhancing images exist which involve capturing corresponding near infrared (NIR) images and transferring the details and contrast of the NIR images based on a mask obtained from the saturation and luminance channels of a visible image (i.e., visual image). However, this method fails under low light conditions. Another method of enhancing low light images includes using NIR images captured with a flash. Such methods completely depend on noise-free and high contrast NIR images captured from a dual camera system by removing an IR cut filter (IR cutoff filter).
Visible images have a natural look comfortably viewable by users using the human eye. NIR images, though effective in displaying the temperature (e.g. heat) of objects (such as humans, cars, or fires), do not look natural. As described, an image capturing device may utilize one or more sensors operating in two different wavelength regions: visible wavelength region (e.g., red, green, and blue (RGB)) and the NIR wavelength regions in order to maximize quality of the captured image during processing.
Although various methods for combining, fusing, the visible image details and the NIR image details exist, such methods apply fusion techniques to the entirety of the images. There exists several situations where fusing a large amount of the details of the NIR image with the visible image may result in an undesired combined image.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.